Internal Gear Pump

ABSTRACT

An internal gear pump comprises an internal gear, a pinion eccentrically positioned in the internal gear and configured to mesh with the internal gear, a cover configured to close an installation space of the internal gear pump, and positioned on end sides of the pinion and the internal gear, a pump outlet leading through the cover, and a non-return valve positioned in the pump outlet in the cover and configured to open to allow flow out of the internal gear pump, and further configured to shut to disallow a return flow through the pump outlet into the internal gear pump.

This application claims priority under 35 U.S.C. §119 to patent application no. DE 10 2013 211 615.2, filed on Jun. 20, 2013 in Germany, the disclosure of which is incorporated herein by reference in its entirety.

The disclosure relates to an internal gear pump. It is provided, in particular, as a hydraulic pump instead of usually used piston pumps in slip-controlled vehicle brake systems. Hydraulic pumps of this type are often called recirculating pumps, even if this is not necessarily correct. In slip-controlled hydraulic vehicle brake systems, a pump outlet, that is to say a pressure side of a hydraulic pump, is connected to a brake line which leads from a brake master cylinder to wheel brake cylinders. A brake pressure which is generated by way of actuation of the brake master cylinder prevails at the pump outlet.

BACKGROUND

Internal gear pumps have an internal gear, that is to say an internally toothed gearwheel, and a pinion, that is to say an externally toothed gearwheel, which is arranged eccentrically in the internal gear and meshes with the internal gear. The designation of the gearwheels as pinion and as internal gear serves to distinguish them. By way of rotation of driving of one of the two gearwheels, usually the pinion, the other gearwheel is also driven and the gearwheels convey fluid, in particular liquid, brake fluid in vehicle brake systems, in tooth spaces of the gearwheels from a suction side to a pressure side of the internal gear pump. This is known and is not to be explained in greater detail here.

Patent DE 196 13 833 B4 discloses one example of an internal gear pump of this type which is not provided, however, for hydraulic vehicle brake systems, but rather for hydraulic machines, in particular construction machines. In a crescent-shaped pump space which is delimited on the inside by the pinion and on the outside by the internal gear and extends in a circumferential section between the gearwheels of the internal gear pump, in which crescent-shaped section the gearwheels do not mesh with one another, the known internal gear pump has a separating piece, against the inner side of which tooth tips of teeth of the pinion bear and against the outer side of which tooth tips of teeth of the internal gear bear. The separating piece divides the pump space into a suction space which communicates with a pump inlet and into a pressure space which communicates with a pump outlet. On account of the typical crescent shape or semi-crescent shape, separating pieces of internal gear pumps are often called a crescent piece. A further designation is a filler piece. Internal gear pumps having a separating piece in the pump space are also called crescent pumps. Internal gear pumps without a separating piece which are also called annular gear pumps are also known. The disclosure can be realized both in a crescent pump and in an annular gear pump.

In a slip-regulated hydraulic vehicle brake system, an internal gear pump requires a non-return valve on or in the pump outlet, which non-return valve prevents, in the case of a stationary pump, that is to say when the slip control is not in operation, brake fluid flowing through the pump outlet into the internal gear pump and from a pump inlet out of the internal gear pump again counter to the conveying direction of the internal gear pump upon actuation of the brake master cylinder, as a result of which a brake pressure which is built up by way of actuation of the brake master cylinder is dissipated and a brake pedal would yield.

SUMMARY

The internal gear pump according to the disclosure has a cover for closing an installation space of the internal gear pump on an end side of the pinion and of the internal gear, it not being necessary for the cover to be arranged directly next to the pinion and the internal gear, but it rather being possible for one or more components to be situated between the cover on one side and the pinion and the internal gear on another side. The installation space of the internal gear pump is, for example, a depression in a hydraulic block of a slip-controlled vehicle brake system, into which the internal gear pump is installed, or an interior space of a pump housing, it being possible for a hydraulic block, into which an internal gear pump is installed, to be considered to be a pump housing of the internal gear pump. In particular, an installation space which is open only on one end side is provided for the internal gear pump, the other end side of which installation space is closed. The cover preferably but not necessarily closes the installation space sealingly.

According to the disclosure, a pump outlet of the internal gear pump leads through the cover and there is a non-return valve in the pump outlet in the cover, which non-return valve can be flowed through out of the internal gear pump and shuts counter to a return flow through the pump outlet into the internal gear pump. When the internal gear pump is at a standstill, the non-return valve prevents throughflow of the internal gear pump counter to its conveying direction from the pump outlet to the pump inlet. If the internal gear pump is used as a hydraulic pump of a slip-controlled, hydraulic vehicle brake system, the non-return valve prevents, in the case of a stationary internal gear pump, brake fluid flowing through from the brake master cylinder of the internal gear pump counter to its conveying direction upon actuation of the brake master cylinder, a throughflow of this type of the internal gear pump counter to its conveying direction and/or through the pump outlet into the internal gear pump being called a return flow.

The disclosure has the advantage of space-saving accommodation of a non-return valve in the pump outlet in the cover of the internal gear pump.

The subject matter of the disclosure provides advantageous refinements and developments.

One preferred refinement of the disclosure provides that the non-return valve has a damper for pressure oscillations of fluid in the cover of the internal gear pump, which fluid is conveyed by the internal gear pump. A space or volume, in which the non-return valve is accommodated, a movable, in particular sprung and/or elastic damper body or a small throughflow cross section in the pump outlet, for example in the manner of a throttle or orifice plate, can have a damping effect. The list is by way of example and is not conclusive.

Another preferred refinement of the disclosure provides that the internal gear pump has a filter in the pump outlet, which filter is arranged between the gearwheels of the internal gear pump and the non-return valve as viewed in the flow direction. The filter prevents solid particles, that is to say chips, particles, etc., passing out of the internal gear pump into the non-return valve, where they can lead to a leak of the non-return valve. Refinements of the internal gear pump according to the disclosure with the filter in the pump outlet are also conceivable without a non-return valve.

One development of the disclosure provides an arrangement of the filter in a pressure field. The pressure field is a typically flat, pressure-loaded depression which is situated on a side of a rotationally fixed and axially movable axial washer, which side faces away from the pinion and the internal gear, which depression extends in the circumferential direction in an arcuate or crescent-shaped manner over approximately the region or a part of the region of the pump space between the pinion and the internal gear. The pressure loading of the axial washer on the outer side loads the axial washer into bearing contact with end sides of the pinion and the internal gear, in order to seal the pump space laterally. The seal is not necessarily hermetically tight, but rather the axial washer bears against the end sides of the pinion, the internal gear and, if present, a separating piece, in a comparable manner to a hydrodynamic axial plain bearing, limited leakage out of the pump space between the pinion and the internal gear on one side and the axial washer on the other side being acceptable. A satisfactory compromise is to be found between low friction and satisfactory sealing action. Axial washers are also called thrust washers or control washers or plates. A washer or plate shape is not necessary for the disclosure.

One development according to the disclosure provides that the filter which is arranged in the pressure field has a supporting element for a pressure field seal, which supporting element supports the pressure field seal from the inside. The pressure field seal is a seal which encloses the pressure field and seals on the circumference. Slip-controlled hydraulic vehicle brake systems are evacuated for filling, before they are filled with brake fluid, in order to avoid inclusions of air. The evacuation can cause a vacuum in the pressure field. The supporting element of the filter according to the disclosure prevents the pressure field seal in the pressure field being displaced from the circumference of the pressure field to the inside and holds the pressure field seal in its position which encloses the pressure field on the circumference.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following text, the disclosure will be explained in greater detail using one embodiment which is shown in the drawing, in which:

FIG. 1 shows an axial section of an internal gear pump according to the disclosure, and

FIG. 2 shows an enlargement of a detail according to rectangle II in FIG. 1.

DETAILED DESCRIPTION

The internal gear pump 1 according to the disclosure which is shown in FIG. 1 has a pump shaft 2 which is mounted rotatably in a cover 4 by way of a bearing, a ball bearing 3 in the embodiment. The cover 4 is a cylindrical part with a flange 5 on one side. It has an axially parallel through hole 6, the diameter of which is stepped multiple times, for guiding through the pump shaft 2, which through hole 6 is eccentric in the cover 4. A gearwheel which is called a drive wheel 7 here is pressed or arranged in a rotationally fixed manner in some other way onto an end of the pump shaft 2 which projects out of the cover 4. The drive gear 7 meshes with a gearwheel which is called a driving gear 8 here and can be driven by way of an electric motor (not shown), optionally with a gear mechanism connected in between.

An externally toothed gearwheel which is called a pinion 9 here is arranged on the pump shaft 2 on another side of the ball bearing 3 to the drive gear 7. The pinion 9 is arranged on the pump shaft 2 in an axially displaceable and rotationally fixed manner; in the embodiment, the axial displaceability and rotational fixing is achieved by way of a four-cornered shaft 10, the disclosure not being restricted to this possibility. The pinion 9 is situated in an internally toothed gearwheel which is called an internal gear 11 here, is arranged in one plane with the pinion 9 and is the same width as the pinion 9. The internal gear 11 is coaxial with respect to the cylindrical cover 4 and eccentric with respect to the pump shaft 2 and with respect to the pinion 9, with the result that the pinion 9 and the internal gear 11 mesh with one another. In the case of a rotational drive of the pinion 9 with the pump shaft 2, the pinion 9 also rotationally drives the internal gear 11 which meshes with it. The internal gear 11 is pressed into a bearing ring 12 which is mounted rotatably in the manner of a plain bearing in a hydraulic block 15.

The pinion 9 and the internal gear 11 enclose a crescent-shape pump space 13 between them in a circumferential section, in which they do not mesh with one another. A semi-crescent-shaped separating piece is arranged in the pump space 13, which separating piece divides the pump space 13 into a suction space and a pressure space. The separating piece is the same width as the pinion 9 and the internal gear 11. The separating piece which is also called a filler piece or, on account of its shape, a crescent is situated outside the sectional plane and therefore cannot be seen in the drawing. By way of rotational driving of the pinion 9 and the internal gear 11, the internal gear pump 1 conveys fluid, brake fluid in the embodiment, from the suction space in tooth spaces of the pinion 9 and the internal gear 11 on the inside and outside along the separating piece into the pressure space.

A seal arrangement with a sleeve seal 16, a supporting ring 17 and a secondary seal 18 is arranged between the ball bearing 3 and the pinion 9, which seal arrangement seals the pump shaft 2 in the cover 4. The sleeve seal 16 is trumpet funnel-shaped and is arranged in such a way that it is loaded against the pump shaft 2 in the case of any pressure loading. The supporting ring 17 which is situated between the ball bearing 3 and the sleeve seal 16 has an annular end face which is curved concavely in accordance with a curvature of the sleeve seal 16 and against which the sleeve seal 16 bears. The secondary seal 18 is a sealing ring which is arranged in an end groove of an annular step of the through hole 6 in the cover 4. The secondary seal 18 is situated on an outer circumference of the sleeve seal 16 on a side which lies opposite the supporting ring 17 and clamps an outer edge of the sleeve seal 16 between itself and the supporting ring 17.

An axial washer 19 which bears against end sides of the pinion 9, the internal gear 11 and the separating piece is situated between the seal arrangement 16, 17, 18 on one side and the pinion 9 and the internal gear 11 on the other side. The axial washer 19 has a through hole for the pump shaft 2. The axial washer 19 is rotationally fixed and axially movable. In plan view, the axial washer 19 has the shape of a circular segment which is greater than a semicircle, a step being cut out of the circular segment at one corner. The axial washer 19 covers the separating piece and the pressure space of the pump space 13 on one side.

The cover 4 has a pressure field 20 on an inner side which faces the axial washer 19, that is to say on an outer side of the axial washer 19, which outer side faces away from the pinion 9 and the internal gear 11. The pressure field 20 is a flat depression with an approximately semi-crescent-shaped form which extends approximately over the pressure space of the pump space 13 and over part of the separating piece. The pressure field 20 is enclosed by a pressure field seal 21 which seals the pressure field 20 between the cover 4 and the axial washer 19. Instead of in the cover 4 as illustrated, the pressure field 20 can also be provided in the outer side of the axial washer 19 (not shown). The axial washer 19 has a through hole 22 which leads from the pressure space of the pump space 13 into the pressure field 20. The pressure field 20 communicates with the pressure space of the pump space 13 of the internal gear pump 1 through the through hole 22, with the result that the same pressure prevails in the pressure field 20 as in a pump outlet. By way of the pressure loading in the pressure field 20, the axial washer 19 is loaded into sealing contact with the end sides of the pinion 9, the internal gear 11 and the separating piece. In the manner of a plain bearing, the axial washer 19 bears against the end sides of the pinion 9, the internal gear 11 and the separating piece, but it does not seal hermetically; an optimum or at least favorable ratio is to be selected between friction between the rotating pinion 9 and the rotating internal gear 11 on one side and the rotationally fixed axial washer 19 on the other side and a low leakage, which can be selected substantially by way of size, shape and position of the pressure field 20. An angled-away bore in the cover 4 leads away from the pressure field 20 in an axially parallel manner for a short distance and subsequently radially to the outside to a circumference of the cover 4. The through hole 22 in the axial washer 19 and the angled-away bore in the cover 4 are constituent parts of a pump outlet of the internal gear pump 1. The angled-away bore in the cover 4 opens into an annular groove 23 in the abovementioned hydraulic block 15, which annular groove 23 encloses the cover 4 at the level of the radial part of the angled-away bore. The annular groove 23 is intersected by an outlet bore 24 which is likewise made in the hydraulic block 15 and, like the annular groove 23, is part of the pump outlet. The outlet bore 24 communicates via a separating valve with a brake master cylinder and via pressure build-up valves with wheel brakes. The separating valve, the pressure build-up valves, the brake master cylinder and the wheel brakes are not shown.

The separating valve and the pressure build-up valves are solenoid valves which are installed into the hydraulic block 15, but outside the sectional plane, for which reason they cannot be seen in the drawing. The brake master cylinder and the wheel brakes are situated outside the hydraulic block 15; they are connected by way of brake lines.

On both sides of the opening of the angled-away bore on the circumference of the cover 4 and therefore on both sides of the annular groove 23 in the hydraulic block 15, the cover 4 has two sealing rings 25 which are arranged in the circumferential grooves in the cover 4 and which seal on both sides of the annular groove 23 between the hydraulic block 15 and the cover 4.

On an opposite side of the pinion 9 and the internal gear 11 to the axial washer 19, the internal gear pump 1 has a thrust washer 26 which bears sealingly against the end sides of the pinion 9, the internal gear 11 and the separating piece. The thrust washer 26 is arranged immovable, that is to say in a rotationally, radially and axially fixed manner in the hydraulic block 15. The thrust washer 26 is circular. The thrust washer 26 has an eccentric, cylindrical through hole which is coaxial with respect to the pump shaft 2 and which forms a bearing 27, in which an end of the pump shaft 2 which is remote from the drive gear 7 is mounted rotatably in the manner of a plain bearing. In order to mount the pump shaft 2 in the manner of a plain bearing, a sliding bearing bush (not shown) can be pressed into the hole 27 in the axial washer 26 or can be fastened there in some other way. Anti-friction mounting of the pump shaft 2 by way of an anti-friction bearing (not shown) in the thrust washer 26 is also possible.

By way of the pressure loading of the outer side of the axial washer 19 in the pressure field 20, the axially movable axial washer 19 is loaded against the end sides of the pinion 9, the internal gear 11 and the separating piece, and those end sides of the axially movable pinion 9, of the axially movable internal gear 11 and of the axially movable separating piece which face away from the axial washer 19 are loaded against the facing inner side of the thrust washer 26, with the result that the end sides of the pinion 9, the internal gear 11 and the separating piece also bear sealingly against the thrust washer 26. Here too, the contact is in the manner of a plain bearing, and the seal is not hermetic, but rather has a leak.

The hydraulic block 15 has a stepped blind bore as installation space 28 for the internal gear pump 1, into which blind bore the gear pump 1 is inserted and is fastened, for example, by way of caulking. The hydraulic block 15 is part of a slip control means (not shown) of a hydraulic vehicle brake system. The hydraulic block 15 is a rectangular part which is made from an aluminum alloy and has a second depression as installation space 28 for a second internal gear pump 1 and further depressions for hydraulic structural elements of the slip control means. Structural elements of this type are solenoid valves and hydraulic accumulators (not shown). The abovementioned electric motor (not illustrated) is flange-connected to the outside of the hydraulic block 15, on the motor shaft of which electric motor or on a gear mechanism shaft of a gear mechanism which is flange-connected to the electric motor the driving gear 8 is seated which drives the two internal gear pumps 1 via the drive gears 7. The seats for the hydraulic structural elements are connected to one another by way of bores in the hydraulic block 15, as a result of which the hydraulic structural elements (not shown) of the slip control means are connected to one another hydraulically. Fitted with the hydraulic structural elements and provided with the electric motor and further electric, electromechanical and electronic components, the hydraulic block 15 forms a hydraulic assembly and a slip control assembly of the hydraulic vehicle brake system.

A pump inlet which is arranged offset at an angle with respect to the pump outlet 29 can be brought about, like the pump outlet 29, through the cover 4 and the axial washer 19 or, on the bottom of the depression in the hydraulic block 13 which forms the installation space 28, through a through hole in the thrust washer 26. The pump inlet is situated outside the sectional plane and therefore cannot be seen.

The pressure field seal 21 is a sealing ring which encloses the semi-crescent-shaped pressure field 20 with a step-shaped annular cross section. An annular end face of the pressure field seal 21 bears against the outer side of the axial washer 19. Offset to the outside and in the direction of the cover 4 with respect thereto, the pressure field seal 21 has a sealing bead which bears against the bottom of the pressure field 20 in the cover 4. In an annular step on the outside of the pressure field seal 21 and facing the axial washer 19, a supporting ring 30 encloses the pressure field seal 21 and supports the pressure field seal 21 from the outside.

A filter 31 is arranged in the pressure field 20 inside the pressure field seal 21. The filter 31, for example a filter fabric, is encapsulated on its edge by a flange-like frame 32 which is semi-crescent-shaped in a manner which corresponds to the pressure field 20 and/or an inner side of the pressure field seal 21. A clearance within the frame 32, in which the filter 31 is situated, is likewise semi-crescent-shaped, in order to ensure a large filter area. The flange-shaped frame 32 of the filter 31 is smaller than an internal circumference of the pressure field seal 21, with the result that there is a gap 33 (see FIG. 2) on the circumference between the frame 32 of the filter 31 and the pressure field seal 21. The flange-like frame 32 of the filter 31 is flatter than the depth of the pressure field 20, with the result that there is a gap 34 between a side of the frame 32 of the filter 31, which side faces the axial washer 19, and the axial washer 19. The pressure field 20 communicates with the pressure space of the pump space 13 of the internal gear pump 1 through the through hole 22 in the axial washer 19 and the gaps 33, 34 between the frame 32 of the filter 31 and the axial washer 19 and the pressure field seal 21. By way of the pressure loading, the pressure field seal 21 is loaded into sealing contact both with the axial washer 19 and with the circumference and/or the bottom of the pressure field 20 in the cover 4. The gap 33 between the frame 32 of the filter 31 and the axial washer 19 is part of the pressure field 20.

The frame 32 of the filter 31 has a collar 35 which protrudes toward the bottom of the pressure field 20 and bears with an outwardly protruding sealing bead in a sealing manner against a mating collar 14 of the cover 4 in the pressure field 20, which mating collar 14 encloses the collar 35. The collar 35 of the frame 32 of the filter 31 encloses the clearance in the frame 32, in which the filter 31 is arranged.

The frame 32 of the filter 31 forms a supporting element which supports the pressure field seal 21 from the inside. If the hydraulic block 15 is evacuated by way of the internal gear pump 1 before filling of the vehicle brake system with brake fluid, the frame 32 of the filter 31 which forms the supporting element prevents the pressure field seal 21 being displaced into the pressure field 20 to the inside and holds the pressure field seal 21 in its provided position on the circumference of the pressure field 20.

Within the collar 35, a through hole 36 opens into the bottom of the pressure field 20. The through hole 36 penetrates the cover 4 of the internal gear pump 1 in an axially parallel manner. As viewed from the pressure field 20, the through hole 36 first of all widens conically with the formation of a valve seat 37 and subsequently by way of two annular steps. A non-return valve 38 is arranged in the through hole 36, which non-return valve 38 has a disk-shaped valve body 39 with a ball ring-shaped bearing face 40 which interacts with the valve seat 37, and a valve stem 41.

The valve stem 41 protrudes into a tubular damper body 42 which has a transverse wall 43 with a hole in its interior, through which hole the valve stem 41 reaches. The hole in the transverse wall 43 of the damper body 42 is larger than the valve stem 41, with the result that there is a passage.

On a side which faces away from the pressure field 20, the stepped through hole 36 in the cover 6 is closed in a pressure-tight manner by way of a cap 44. The cap 44 is pressed into the through hole 36 and is held in a pressure-tight manner, for example, by way of a calked connection (not shown). The cap 44 bears against an annular step of the through hole 36. The damper body 42 is movable in the through hole 36; a spring element 45 in the form of a compression coil spring which is arranged between the cap 44 and the transverse wall 43 of the damper body 42 loads the damper body 42 and, via the latter, the closing body 39 of the non-return valve 38 against the valve seat 37. On account of its movability in the through hole 36, the damper body 42 damps pressure oscillations of brake fluid which occur during operation of the internal gear pump 1 as a result of the non-return valve 38.

The closing body 39 of the non-return valve 38 and of one end of the damper body 42 which faces it are enclosed by an annular channel 46 which is configured as an undercut in the through hole 36 adjacently to the valve seat 37. The pump outlet 29 which runs radially in the cover 4 opens into the annular channel 46. The pump outlet 29 is offset axially with respect to the annular channel 46, with the result that the pump outlet 29 intersects the annular channel 46. This results in a step with a small through flow cross section, which step likewise damps pressure oscillations in the pump outlet.

The through hole 22 in the axial washer 19, which through hole 22 communicates with the pressure space in the pump space 13 of the internal gear pump 1, the pressure field 20, the clearance in the frame 32 of the filter 31, the through hole 36 as far as the damper body 42, the annular channel 46 which encloses the closing body 39 of the non-return valve 38, the annular groove 23 in the hydraulic block 15, which annular groove 23 encloses the cover 4 between the sealing rings 25 and into which annular groove 23 the radial part of the pump outlet 29 opens, and the outlet bore 24 in the hydraulic block 15, which outlet bore 24 intersects the annular groove 23, form the pump outlet. 

What is claimed is:
 1. An internal gear pump comprising: an internal gear; a pinion eccentrically positioned in the internal gear and configured to mesh with the internal gear; a cover configured to close an installation space of the internal gear pump, the cover positioned on end sides of the pinion and the internal gear; a pump outlet defined through the cover; and a non-return valve positioned in the pump outlet in the cover and configured to open to allow a fluid flow out of the internal gear pump, and further configured to shut to prevent a return fluid flow through the pump outlet into the internal gear pump.
 2. An internal gear pump according to claim 1, wherein: the cover defines a stepped hole; and a valve seat of the non-return valve is defined on a step of the stepped hole.
 3. An internal gear pump according to claim 1, wherein the non-return valve includes a damper configured to damp pressure oscillations of fluid conveyed by the internal gear pump.
 4. An internal gear pump according to claim 3, wherein the non-return valve further includes at least one of an elastic damper body and a spring damper body.
 5. An internal gear pump according to claim 3, wherein the pump outlet in the cover has a through flow cross section configured to damp pressure oscillations of the fluid conveyed by the internal gear pump.
 6. An internal gear pump according to claim 1, further comprising: a filter positioned in the pump outlet in the cover, wherein the filter is also positioned upstream, relative to a direction of fluid flowing out of the internal gear pump, of the non-return valve.
 7. An internal gear pump according to claim 6, further comprising: a rotationally fixed and axial movable axial washer positioned between, on one side, the pinion and the internal gear and, on another side, the cover, wherein the internal gear pump is configured to develop a pressure field on an outer side facing away from the pinion and the internal gear, the pressure field forcing the axial washer, in the case of pressure loading, into bearing contact with the end sides of the pinion and the internal gear; wherein the filter is positioned in the pressure field.
 8. An internal gear pump according to claim 7, further comprising: a pressure field seal configured to enclose the pressure field, wherein the filter includes a supporting element configured to support the pressure field seal on an inside of the pressure field seal.
 9. An internal gear pump according to claim 8, wherein the filter and the supporting element are formed as one piece.
 10. An internal gear pump according to claim 8, wherein the filter includes a collar. 